1. Field of the Invention
The present invention relates to a filter for removal of leucocytes coated with a natural polymer of chitosan. More particularly, the invention relates to a filter for removal of leucocytes prepared by applying a natural polymer of chitosan on ultrafine non-woven fabric, wherein said polymer has a good blood compatibility while avoiding negative side-effects in a human body. The filter for removal of leucocytes of the invention has a high removal rate of leucocytes with good recovery of platelets and red blood cells.
2. Description of the Prior Art
Blood occupies about 6 to 8%by weight of human body, and about 40 to 45% by volume of blood is solid phase and the rest is liquid phase. The solid cell components of blood consist of red blood cells (RBC), leucocytes and platelets, and the liquid components of blood, so-called plasma, consist of a solution of plasma protein such as fibrinogen, albumin and gamma-globulin, and organic and inorganic salts in water. As disclosed above, blood is important and valuable as a structural component of the human body as well as functional component. Recently, a trend in blood transfusion has been changing from transfusing a whole blood to a active transfusion of only desired blood components, and such transfusion is commonly utilized in blood transfusion therapy. The blood components transfusion therapy has an advantage in that it is possible that sufficient amounts of particular blood components are provided to a patient in need of such components. Additionally, it is possible to use a single unit of donated blood in larger patients, thereby avoiding waste of blood resources.
After transfusion of a blood preparation of red cell or platelet concentrates as well as a fresh whole blood, leucocytes contained in the preparation may result in several side effects such as non-hemolytic pyrexia and transfusion refractoriness due to forming of anti-leucocyte antibodies. In particular, repeated transfusions of platelet concentrates frequently leads to alloimmunization against histocompatible antigen of leucocytes contained therein. Thus, in order to reduce such leucocyte-associated post-transfusion complications, it is desirable to remove leucocytes from platelet concentrates.
Amongst the various techniques to remove leucocytes from blood, platelet separation aphersis has been recommended since it can reduce the number of donors. Also, conventional methods such as centrifugal settlements and washing with physiological saline may be utilized in the removal of leucocytes. Recently, a filtration through a filter has been developed and is beginning to replace centrifugation and washing processes. Since the filtration is conducted by using a disposable filter, inflammation can be avoided. Also, by using gravity, separate additional devices are unnecessary. This filtration process has advantages in that removal efficiency of leucocytes is high, and the time required is short.
Seyfert et al. disclosed that cell adhesion was increased by coating a microscope slide matrix with polycations. They reported that cell adhesion rate on the matrices was influenced more by electrostatic interaction due to surface charge rather than by surface tension (See, S. Seyfert, A. Voigt and D. Kabbeck-Kupijai, "Adhesion of Leucocyte to Microscope Slides as Influenced by Electrostatic Interaction", Biomaterials, Vol. 16, No. 3, pp 210-207, (1995)).
Nishimura et al. disclosed that when non-woven fabric of polyester is used to remove leucocytes, as the fibre diameter of the fabric is made smaller, the removal rate of leucocytes becomes higher. Also, they reported that non-woven fabric having its surface coated with a random copolymer of hydroxyethylmethacrylate and diethylaminoethylmethacrylate has cationic potential [See, T. Nishimura, T. Kuroda, Y. Mizoguchi, H. Watanabe, H. Rikumaru and M. Umegae, "Advanced Method for Leucocyte Removal by Blood Filtration" in "The Role of Leucocyte Depletion in Blood Transfusion Practice", B. Brozovic ed., Blackwell Scientific Publications, Oxford (1989) pp 35-40].
Further, Bruil et al. carried out an experiment in which non-woven fabrics of polyurethane coated with poly(ethyleneimine) were used as a filter in order to investigate its effect on the leucocytes adhesion during filtration, and they confirmed that leucocytes adhered to the surface of the filter through selective interaction with its amine group [See, A. Bruil, H. A. Oosterom, I. Steneker, B. J. M. Al, T. Beugeling, W. G. van Aken, and J. Feijin, "Poly(ethyleneimine) Modified Filters for the Removal of Leucocytes from Blood", J. Biomed. Mat. Res., Vol. 27, pp 1253-1268 (1993)].
Recently, filters for removal of leucocytes have been clinically utilized, and devices and methods for blood filtration using a fiber filter having surface modified with various polymers are disclosed in the many patent publications (See, U.S. Pat. No. 4,923,620, U.S. Pat. No. 4,880,548, U.S. Pat. No. 4,701,267, EP 0 397 403 A1, EP 0 408 462 A2 and EP 0 406 485 A1). However, no patent publication teaches that a non-woven fabric having its surface coated with chitosan may be used as a blood filter.
According to the present invention, excellent effects can be accomplished by using a natural biocompatible polymer, not using a synthetic polymer as a coating solution for non-woven fabric.
The present inventors have carried out many investigations in order to increase the biocompatibility of the filter for blood filtration. As a result, it has been found that a filter having improved properties can be obtained by newly applying chitosan as a coating material on non-woven fabric which have been used as a conventional filter material. In accordance with the present invention, there is provided a filter for removal of leucocytes having a sufficient removal efficiency of leucocytes and recovery of red blood cells or platelets without causing any side effects in the human body. The above result is consistent with a removal rate of leucocytes of at least 95% and a recovery of red blood cells of at least 90% and a recovery of platelets of at least 90% as recommended by the American Association of Blood Banks.